From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: "Belted Magnums"
Organization: Hewlett-Packard Fort Collins Site
webdw@mvutd.att.com wrote:
: Some high pressure rifle cartridges have belts near base of cartridge
: (built up areas) for extra strength;
I disagree. Pressure with modern cartridges whether belted or not is
about the same; 50 to 55 thousand psi. The belt does not significantly
increase the case strength. Pressure is the same at all points of the
case; head, body, shoulder and neck, so making the first tenth of an
inch in front of the extractor groove thicker may result in that part
being stronger, but the rest of the case wall thickness remains the same.
Without that belt on the original H & H case using it, the firing pin's
force will drive the case far enough into the chamber that the shoulder
will be set back. With the shoulder set back, the chance of head
separation greatly increases. With the case too far forward in the
chamber when the powder ignites, the increase of pressure will press the
shoulder and body walls hard against the chamber walls, but the head will
be pushed back far enough to separate the brass at the thinnest point
not grabbing the chamber wall. That point is right in front of the
belt on H & H type of cases; about one tenth of an inch in front of the
extractor groove on normal rimless cases.
That belt acts as a rim to keep the case head against the bolt face to
prevent head separation. The original belted cartridges from H & H in
the early 1900s had about 45K psi. For example, the ballistics of the
H & H Super 30 equalled that of the then fairly new .30-06; both shot
the same weight bullet at almost exactly the same speed. The reason
H & H had to use a case longer than the '06 case was to get enough long
cordite powder sticks inside to duplicate the '06s velocity. That long
case needed a shallow shoulder angle to facilitate cordite, long-stick
powder insertion. The only way headspace could be maintained was to
put a belt on the case head. A standard, rimmed case could have been
used, but rimmed cases do not feed reliably in bolt action rifles.
Their double rifle version of this cartridge had its rimless, belted
head replaced with a rimmed, or `flanged' case.
This belief that belted cases are used for cartridges with higher
pressures is widespread. With due respect to those so thinking, it
is just another myth in reality. My intention is not to burst bubbles,
but instead properly inflate them.
BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Belted cases
Organization: Hewlett-Packard Fort Collins Site
Belted cases were designed by Holland & Holland (great British rifle and
shotgun firm) in the early 1900s. They were needed to headspace their
newly introduced Super 30 cartridge that had a very small shoulder angle.
Called the .300 H & H Magnum in the USA, it originally used stick Cordite
powder and the small case shoulder angle was needed to enable stuffing the
Cordite in the cartridge. Later, H & H made a .375 and other calibers on
this same case.
In 1935, Ben Comfort won the prestigious Wimbledon Cup Match (1000 yards
and scope sights) at the USA National Championships using a custom-built
Super 30 and a Litchert target scope and set a record. That single event
caused most shooters to then consider the .300 H & H Magnum `the' long-range
hunting cartridge and nothing else was considered. Although the .300 H & H
was about equal in power to the venerable .30-06 as loaded by H & H with
cordite powder, and being kept at moderate pressure levels so it wouldn't
blow up H & H, Rigby, Wesley Richards, Jeffery, and other makes used in
the hottest climates in Africa, USA companies loaded it to the same maximum
pressures used with the .30-06. That caused the .300 H & H bullets to leave
the muzzle at about 200 fps faster than they did in the '06.
Well, that made most folks think the belted case cartridges was the ultimate
in power and their egos were spurred to such great uncontrolled lengths by
companies marketing and chambering rifles for this cartridges. Although
Charles Newton had 30 caliber cartridges using rimless cases that fed much
easier through bolt action magazines and were actually more accurate plus
shooting equal bullets at the same velocities as the Super 30, that didn't
matter. Everybody had to have the cartridge that was used to win the big
long-range match at the Nationals. Griffin & Howe built that rifle for
Ben Comfort and they immediately got more orders for custom .300 H & H
Magnums than they ever dreamed of. Shortly thereafter, Winchester chambered
their brand new Model 70 hunting and target rifles for it. But several years
went by before powders slow enough to get highest velocity were available to
handloaders.
Since about 1936, most folks have felt that if the case didn't have a belt
on it, it wasn't very powerful. Such a miscarriage of information has never
been promoted throughout the shooting sports; except perhaps Browning's BOSS.
Most belted cases headspace on their shoulder after they are first fired
anyway. If they don't, they should. Otherwise, case life is very short
and as few as 3 or 4 reloads per belted case is common as folks set their
shoulder back too far when full-length sizing. Modern day `magnum' cartridges
don't need that belt; they have enough shoulder to hold headspace very easy.
The exceptions are straight-wall cases like the .458 Win. Mag. that do need
something to headspace on so that belt does work for such cases. Most folks
won't buy a rifle chambered for a magnum cartridge unless the cases have a
belt on 'em. They're convinced that belt means `power' and without it, there
is no such thing. Rifle makers are trapped into this same thing and they
aren't about to change it; rifle sales would drop.
Such a tragedy indeed that folks have gotten wrapped up in belted cases for
powerful cartridges when a rimless one of the same capacity would be more
accurate, feed easier and case life for the average reloader would quadruple.
BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Belted cases
Organization: Hewlett-Packard Fort Collins Site
James Warren (jdw@unislc.slc.unisys.com) wrote:
: Would you please explain why a non-belted case would be more accurate
: than the same case without a belt?
There's two reasons.
With the larger diameter bolt face and case head belted cases have, that
means any case with an out-of-square head can impact the bolt face further
from center as the round fires. This means the same amount of force is now
a greater distance from bolt face center than an equal capacity/length
rimless case will produce. With the force further from center, receiver
and barrel whip will be of a greater magnatude; the muzzle will be further
away from its neutral position and the bullet will exit at a greater angle
from the line of sight. That means it will strike further away from where
it was aimed. This is the reason why `magnums' tend to throw a shot quite
aways from group center every once in a while. Rimless cases don't do
this nearly as often and when they do, the distance from group center that
wide shot goes isn't nearly as far.
Belted cases are harder to make with very uniform body wall thicknesses.
Rimless cases of the same length and capacity are typically more uniform
in body wall thickness. When the body wall thickness is non-uniform
around the case, the energy chamber is off-center from the chamber and
the force is not directed backwards against the bolt face center as uniform
as with rimless cases. This is the reason why PPC cases are favored for
benchrest matches; their energy chamber is well centered on the chamber's
axis due to their case wall thickness being very uniform all the way around
the case.
: As for increased case life, it seems to me that they would be the same if
: you follow the same resizing procedure (neck size only or just bump the
: shoulder a bit if necessary).
Neck sizing doesn't work for belted cases; it's not going to produce the
best accuracy and most so-resized belted cases won't rechamber in the same
rifle anyway. Whenever someone thinks neck sizing does work, I'm convinced
they haven't shot enough test groups with enough shots per group to be
significantly worthwhile.
Most belted case rifles need their fired cases sized all the way back to
the belt by the full-length die. That's because most folks load these cases
too hot and the unsupported case immediately in front of the belt expandes
enough that it won't chamber fully, even after typical full-length sizing.
Most folks think the bolt won't close because the shoulder isn't set back
far enough, so they screw the FL die down, then resize again. When this
happens, the shoulder gets set back further and further as the die finally
gets the body diameter in front of the belt small enough to let the case
be chambered. When so-sized cases are fired, the shoulder being back many
thousandths from the chamber's shoulder blows forward and the pressure ring
thins. After only a few FL sizings and firings using such practices, the
case will have a head separation. I'm convinced this is the most common
cause of short belted case life so many folks have. The cure is to cut
the powder charge a couple of grains and set the FL sizing die in the press
only far enough to set the fired case's shoulder back about .001-in. Case
life will greatly increase and accuracy will get better, too. Plus, the
peak pressures are going to be back down for what the case and rifle was
designed for in the first place. Had I not observed dozens of belted case
rifles having these case life problems, I would not have believed it to be
a reality.
BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbit)
Subject: Re: Reload question - brass longevity
Organization: Hewlett-Packard Fort Collins Site
Paul Donehue (pjd@Eng.Sun.COM) wrote:
: In reading a Lyman reloading manual, it mentions
: the banded magnum shells are only good for around 3 loadings. Is this number
: realistic or overly conservative on their part so as to avoid being sued?
I've no idea why Lyman says belted cases last about 3 reloads. I've got
as many as 21 on one batch of cases and full-power loads were used.
Most folks don't understand the case sizing issues regarding belted
cases. If they full-length resize, more often than not they set the
shoulder back way too far and that really shortens case life. Belted
cases when new often have their shoulders 25/1000ths of an inch back
from the chamber's shoulder when they are fired. Some stretching may
well occur with the first firing. When full-length resized and the die
touches the shell holder, the shoulder is probably set back too far and
this just happens every time the case is fired/sized. No wonder they
last less than 5 reloads. If the die is backed up in the press to set
the fired case shoulder back only one or two thousandths of an inch,
case life will be around 20 reloads or more.
Backing off the full-length sizing die will solve the case stretching
problem, but it often exposes another problem. If the belted case is
loaded too hot (too much powder for the load), the case diameter in
front of the belt may not get sized down enough as the base of the die
doesn't touch it. That may prevent the case from easily chambering
in the normal, out-of-round chamber. So, to solve this problem, you
must screw the die down. But that sets the shoulder back too far.
Reloading belted cases is not as simple as regular rimless cases. If
one notes all of the dimensional changes their belted cases go through
from firing a new case to several reloadings, they'll understand the
grief that many people have due to short belted case life.
Although neck sizing may extend the case life, it typically reduces
accuracy with belted cases.
BB

From: Gale McMillan <gale@mcmfamily.com>
Newsgroups: rec.guns
Subject: Re: Belted cartridge design - headspace - cartridge construction
Date: 19 Aug 1998 22:30:00 -0400
funkraum wrote:
> ...
The belted cartridge originated in England and was adopted for the use
in long tapered cases that would not hold the head space on the shoulder
due to the shape so they head spaced on the belt. It became a status
symbol and while there has been some fine beltles magnums like the
Newton and Lazeroni the public still associates the belted case with
quality.The belt has nothing to do with the strength of the case as it
is at the web where the case is solid and reduces down behind the belt
where high pressure will expand the primer pocket. Had the belt extended
to the end of the case it may have increased the strength marginally.
Gale McMillan